The present invention relates to a method and an according device for driving a radiation emitting device, such as light emitting diode (LED) which is to be used for a wide range of modulation frequency.
LEDs are generally known. These kind of diodes transmit electromagnetical radiation with a given wavelength (or colour), which depends on physical characteristics of the LED. Commonly known LEDs transmit light with e.g. red, green, yellow colour or infrared (IR) radiation. LEDs transmitting visible light can be used for for displaying information, such as a process parameter of a device, to a user.
In addition to this, all kinds of LEDs can be used for a system including a light transmitter and a light receiver. Such systems can also use a light wave conductor and can be used for the transmission of audio-, video- and/or data-information. A preferred application for such a system is a infrared- (IR-) remote control for any kind of devices, such as TV-sets, audio-receivers, videotape-recorders, etc. For transmitting the mentioned information it is necessary to modulate the radiation transmitted by the LED. This can be done e.g with the aid of a pulsed modulation wherein during the duration of a pulse the transmitted radiation is switched on and off with a given modulation frequency, which is called in the further description carrier frequency.
Known IR-remote control systems work in a wide range of carrier frequencies, normally from 30 kHz up to 500 kHz. Often a remote control transmitter is used just for the control of a single device, and thereby it works either in the carrier frequency range of --30 to 40 kHz, or --390 to 500 kHz.
From EP 289 625 B1 there is a remote commander known which can be used for controlling a number of devices by learning commands from other remote commanders.
From the elder (not yet published) German patent application P 43 08 441.9 is a learning remote commander known, which can be used for different kinds of carrier frequencies and which is also able to consider the presence of so-called togglebits.
We have found out that there occur problems, if a remote commander of the type mentioned includes just a single radiation emitting element, such as a LED, or a number of such elements which are driven simultaneously.
It is an object of the present invention to solve the above mentioned problem.